The US Coastguard said on Thursday that the grounding of a Shell oil drilling rig in the Gulf of Alaska in 2012 was in part driven by tax-dodging.

It said Alaska’s tax laws had influenced the decision to tow the drilling rig Kulluk to Seattle for maintenance.

Shell believed the rig would have qualified as taxable property on January 1 2013 if it was still in Alaskan waters.

The Kulluk broke away from its tow in late December 2012 after it ran into a vicious storm — a fairly routine winter event in Alaskan waters.

Multiple attempts to maintain tow lines failed and the vessel ran aground on New Year’s Eve just off Kodiak Island.

Several days before the tow initially broke, the master of the tow vessel Aiviq sent an email to the Kulluk’s towmaster expressing concerns about the conditions.

“To be blunt I believe that this length of tow, at this time of year, in this location, with our current routing, guarantees an ass kicking,” said the email.

The Aiviq’s master and towmaster asked Shell’s marine manager for permission to change course but the request was “not formally granted.”

The coastguard concluded that sufficient evidence existed for the relevant authorities to consider penalties.

Senator Ed Markey said that Shell should be held accountable for its “reckless behaviour” pertaining to its tax-avoidance motivations.

“This report shows Shell ran through every single safety and common sense red light in moving this rig because of financial considerations,” Mr Markey said.

“This kind of behaviour should raise major red flags for any future Arctic drilling plans.”

Environmental groups said the oil industry and government were ill-prepared to deal with oil development in the Arctic Ocean.

“Today’s report again shows that Shell did not appreciate or plan for the risks of operating in Alaskan waters, prioritised financial considerations ahead of safety and precaution and simply disregarded important legal protections,” said conservation group Oceana staff lawyer Mike LeVine.

“The report again confirms what common sense dictates: companies and government agencies are not ready for the Arctic Ocean.”